media: nxp: imx8-isi: Allow num_sources to be greater than num_sink

Allow num_sources (drvdata: num_channels) to be greater than num_sink
(drvdata: num_ports + 1).

ISI support stream multiplexing, such as differentiates multiple cameras
from a single 2-lane MIPI input, or duplicates input stream into multiple
outputs. So num_channels may be greater than num_ports at some platform.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250522-8qxp_camera-v5-2-d4be869fdb7e@nxp.com


Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>